1. Field of the Invention
The present invention relates to the conversion of electrical power into torque and particularly to controllably causing an electrically powered wheel to rotate about a stationary axle without requiring the delivery of electrical energy to the wheel from the vehicle which supports the axle. More specifically, this invention is directed to an electrical drive system wherein the source of electrical current and the electro-mechanical components which convert the source current into torque are housed within the confines of a wheel and especially to such a drive system wherein the command signals from a vehicle mounted control signal generator are optically coupled to the wheel. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use on lightweight vehicles which include a pair of large, rearwardly disposed drive wheels such as, for example, the well known foldable wheelchair. There has been a long standing need for an efficient and reliable drive system which would permit wheelchairs characterized by a dual-planar, tubular frame construction to be motorized. For a discussion of prior efforts to provide motorized wheelchairs, reference may be had to the present inventor's U.S. Pat. No. 5,186,269 and the prior art of record therein.
The solution to the problems incident to retrofitting a manually powered wheelchair with an electomechanical drive disclosed in U.S. Pat. No. 5,186,269 constituted a significant step forward in the art. However, further improvements, and particularly a reduction in complexity with a simultaneous increase in efficiency, have been sought. For example, in the patented system, torque was delivered to the rims of the drive wheels via lever arms having a length which were maximized for the particular chair. Also, a comparatively heavy battery pack was removably suspended from the rear portion of the chair frame thus tending to unbalance the chair.